The invention relates to a process for the storing of drawing data of a CAD drawing system by means of a CAD film-card laser plotter, wherein the vector and/or raster data are stored optically on a film of a microfilm card. The invention relates further to a microfilm card and a CAD film-card laser plotter for implementation of this process.
To output CAD drawings on microfilm, the CAD model data of the drawing are converted in the computer into two-dimensional vector and/or raster data of which the graphical representation of the drawing consists. However, since the CAD model data also contains other additional data with which the computer works, they have to be stored digitally all together on magnetic disks or optical memory disks. Only in this manner has it been possible heretofore to play back all the CAD model data into the working memory of a CAD system at a later time. Hence, for the long-term storage of CAD drawings, it has been necessary heretofore to keep two archives. A film-card archive contains the graphical representation of the drawings and is evaluated with readers and enlargers. In addition, a digital tape or disk archive has to be kept which contains all the binary CAD model data and is used to "play back" the digital model data for the CAD change designs into the working memory. For several reasons, this need to keep two archives/files is extremely expensive with respect to organization and costs. Thus, for example, preservation of the digital data on magnetic tapes or disks requires frequent "refreshing" in order that the data remain satisfactorily preserved. Also, maintenance of the digital data of the various revisions of drawings over a long period of time requires considerable expense. It makes it necessary to keep an additional data base and entails a large economic risk due to the rapid changing of hardware and software systems.
In the case of microfilm cards, it is known to provide, in addition to the film image, a magnetic strip on which additional data belonging to the film image are stored. It is also known to provide on a film image a coding which contains machine-readable data for the identification and classification of the drawing. A feature common to such additional storage fields on microfilm cards is that they serve to store data which are useful for the organizational evaluation of the card archives, e.g. sorting or selecting of cards.
Commonly used for the storing of vector and/or raster data are CAD film-card laser plotters which have a laser exposure station, a development station, an inscription station and a duplication station. For example, such a CAD film-card laser plotter is illustrated in FIG. 3 of EP-A-85108144.8 and explained in the specification. The known CAD film-card laser plotter makes it possible for model data of CAD drawing systems converted into raster data to be exposed on the film of the film card, the film to be developed immediately and the film card to be inscribed. The CAD film-card laser plotter also makes it possible for the original film cards to be duplicated immediately on silver film cards, for which purpose the same inscription and development device is used as for the original film cards.